3Pi+机器人巡线挑战故障：传感器正常时机器人直行无视线路

核心问题点 #

• 转向逻辑完全反向
  现有逻辑中，左传感器检测到黑线时执行右转、右传感器检测到黑线时执行左转，完全和实际需求相反：左传感器压到黑线说明线路在机器人左侧，需要向左转向才能将中线拉回黑线，反之同理。
• 缺少状态兜底处理
  仅设置了三种触发场景，只要不满足这三种条件（比如三个传感器同时在黑线上、同时在白地上、左右同时压黑线），电机就会保持初始的直行状态，不会触发任何转向动作。
• 阈值未绑定实测数据
  固定的10000阈值需要和串口打印的实际读数匹配：白色地面的elapsed_time应小于阈值，黑色线路的elapsed_time应大于阈值，阈值设置错误会导致所有判断条件都无法触发。
• 传感器索引对应关系需要验证
  确认ls_pin数组{左传感器、中传感器、右传感器}的顺序和实际硬件接线完全对应，接线顺序错误会导致所有逻辑失效。

修复后参考代码 #

const int left_sensor_pin = A0;
const int right_sensor_pin = A3;
const int centre_sensor_pin = A2;

// 存储传感器引脚
#define NB_LS_PINS 3
int ls_pin[NB_LS_PINS] = { left_sensor_pin, centre_sensor_pin, right_sensor_pin };

// 时间相关变量
unsigned long start_time;
unsigned long elapsed_time [3];
unsigned long end_time_ls [3];
// 统一定义巡线阈值，方便根据实测调整
#define LINE_THRESHOLD 10000

bool done = false;

# define L_PWM_PIN 10
# define L_DIR_PIN 16
# define R_PWM_PIN 9
# define R_DIR_PIN 15

void setup() {
  Serial.begin (9600);
  pinMode (left_sensor_pin, INPUT);
  pinMode (right_sensor_pin, INPUT);
  pinMode (centre_sensor_pin, INPUT);
  delay(5000);

  pinMode(L_PWM_PIN, OUTPUT);
  pinMode(L_DIR_PIN, OUTPUT);
  pinMode(R_PWM_PIN, OUTPUT);
  pinMode(R_DIR_PIN, OUTPUT);

  digitalWrite(L_DIR_PIN, LOW);
  digitalWrite(R_DIR_PIN, LOW);
}

void loop() {
  // 电容充电
  pinMode (left_sensor_pin, OUTPUT);
  pinMode (right_sensor_pin, OUTPUT);
  pinMode (centre_sensor_pin, OUTPUT);
  digitalWrite(left_sensor_pin, HIGH);
  digitalWrite(right_sensor_pin, HIGH);
  digitalWrite(centre_sensor_pin, HIGH);

  delayMicroseconds(10);
  start_time = micros();

  pinMode (left_sensor_pin, INPUT);
  pinMode (right_sensor_pin, INPUT);
  pinMode (centre_sensor_pin, INPUT);

  bool pins_read [3] = {false, false, false};
  done = false;

  while (done == false) {
    for (int which = 0; which < NB_LS_PINS; which++) {
      if (digitalRead(ls_pin[which]) == LOW && pins_read[which] == false) {
        end_time_ls[which] = micros();
        pins_read[which] = true;
      }
      if (pins_read[0] && pins_read[1] && pins_read[2]) {
        done = true;
      }
    }
  }

  elapsed_time[0] = end_time_ls[0] - start_time;
  elapsed_time[1] = end_time_ls[1] - start_time;
  elapsed_time[2] = end_time_ls[2] - start_time;

  Serial.println(elapsed_time[0]);
  Serial.println(elapsed_time[1]);
  Serial.println(elapsed_time[2]);
  Serial.println("------------------------------");

  // 修正后的电机控制逻辑
  if (elapsed_time[0] < LINE_THRESHOLD && elapsed_time[1] > LINE_THRESHOLD && elapsed_time[2] < LINE_THRESHOLD) {
    // 中线压黑线，直行
    analogWrite(L_PWM_PIN, 100);
    analogWrite(R_PWM_PIN, 100);
  } else if (elapsed_time[0] > LINE_THRESHOLD && elapsed_time[1] < LINE_THRESHOLD && elapsed_time[2] < LINE_THRESHOLD) {
    // 左传感器压黑线，左转
    analogWrite(L_PWM_PIN, 0);
    analogWrite(R_PWM_PIN, 100);
  } else if (elapsed_time[0] < LINE_THRESHOLD && elapsed_time[1] < LINE_THRESHOLD && elapsed_time[2] > LINE_THRESHOLD) {
    // 右传感器压黑线，右转
    analogWrite(L_PWM_PIN, 100);
    analogWrite(R_PWM_PIN, 0);
  } else {
    // 兜底逻辑，可根据需求调整，此处为低速直行找线
    analogWrite(L_PWM_PIN, 50);
    analogWrite(R_PWM_PIN, 50);
  }
}

验证步骤 #

1. 先单独测试传感器，分别将三个传感器放在黑线和白地上，记录串口输出的elapsed_time数值，调整LINE_THRESHOLD为黑白读数的中间值。
2. 空载测试转向逻辑，手动将左传感器放在黑线上，确认左轮停转、右轮转动，机器人向左转向，反之右传感器压黑线时向右转向。

内容的提问来源于stack exchange，提问作者er281